86. A thin circular ring of man "m" and radius "R" is supported by a nail in a vertical plane in uniform vertical gravity. The period of small oscillations of the ring is A) B) RIS C) 2 2R D) 2 87. The theory governing combinations of quarks based on quantum electrodynamics is called A) Baryon theory B) Quantum chromo dynamics D) Lepton theory C) Meson theory 88. 89. The activity of a radioactive sample falls from 600 sto 500 s-1 in 40 minutes. Calculate its half life. A) 152 minutes C) 120 minutes B) 170 minutes D) 192 minutes A gas of molecules has mass m each is in thermal equilibrium at absolute temperature T. Root mean square (r.m.s) speed, average speed and most probable speeds i.e. Vrms: V: are in proportion A) KT/m [3:8/: 2] C)KT/m [3: 8/n: 5] B) kT/m [2: 8/: 3] D) KT/m [3:/8: 2] 90. The system is maintained at equilibrium temperature of 300 K. What is the amount of heat (in eV) needed to increase number of accessible states to 10%? A) 0.5 eV B) 1 eV C) 2 eV D) 1.5 e